Fields (Attributes)

Part of the Object Oriented Programming section of Coddy's Java journey — lesson 6 of 87.

Fields (attributes) are variables that store data inside a class. They are usually private and accessed through getter and setter methods.

Declaring fields

public class Person {
    private String name;
    private int age;
}

Adding getters and setters

public class Person {
    private String name;
    private int age;
    
    public String getName() {
        return this.name;
    }
    
    public void setName(String name) {
        this.name = name;
    }
    
    public int getAge() {
        return this.age;
    }
    
    public void setAge(int age) {
        if (age >= 0) {
            this.age = age;
        }
    }
}

Using the class

Person person = new Person();
person.setName("Alice");
person.setAge(25);
System.out.println(person.getName());  // Alice

Making fields private is called encapsulation. It protects data by controlling access through methods, allowing you to add validation in setters.

Challenge

Medium

Create a BankAccount class with private fields and getter methods:

Private fields: accountName (String) and balance (double)
A constructor to set both fields
Getter methods for each field
deposit() method to add money
withdraw() method that returns "Success" or "Insufficient funds"

Cheat sheet

Fields (attributes) are variables that store data inside a class. They are usually private and accessed through getter and setter methods.

Declaring private fields:

public class Person {
    private String name;
    private int age;
}

Adding getters and setters:

public class Person {
    private String name;
    private int age;
    
    public String getName() {
        return this.name;
    }
    
    public void setName(String name) {
        this.name = name;
    }
    
    public int getAge() {
        return this.age;
    }
    
    public void setAge(int age) {
        if (age >= 0) {
            this.age = age;
        }
    }
}

Using the class:

Person person = new Person();
person.setName("Alice");
person.setAge(25);
System.out.println(person.getName());  // Alice

Making fields private is called encapsulation. It protects data by controlling access through methods, allowing you to add validation in setters.

Try it yourself

import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        String name = scanner.nextLine();
        double initial = Double.parseDouble(scanner.nextLine());
        double deposit = Double.parseDouble(scanner.nextLine());
        
        BankAccount account = new BankAccount(name, initial);
        
        System.out.println("Account: " + account.getAccountName());
        System.out.println("Balance: " + account.getBalance());
        
        account.deposit(deposit);
        System.out.println("After deposit: " + account.getBalance());
        
        String result = account.withdraw(2000);
        System.out.println("Withdraw 2000: " + result);
        System.out.println("Final Balance: " + account.getBalance());
    }
}